At present, there are various power tools having accessory clamping mechanism on the market. One such power tool has a working mandrel for driving the accessory, the accessory being fixed between a holding portion on one end of the working mandrel facing the tool and a fastening member; and a mechanism for moving the fastening member between a released position in which the fastening member is removed from the working mandrel and a clamped position in which the fastening member is clamped against the holding portion by a spring element. The fastening member has a clamping shaft inserted into the working mandrel. The clamping shaft is held in the clamped position by a locking assembly arranged in the working mandrel and can be removed in the released position. The locking assembly comprises a collar and clamping members, and the clamping members are radially and movably held in a recess portion of the collar and abut against the collar. Each of the clamping members has an inclining surface at one side facing the tool for mating with the inclining surface of the collar so that the movement of the collar abutting against the inclining surfaces of the clamping members can cause an impact on the clamping member towards the center thereof.
The working principle of the power tool lies in that the working mandrel swings around the axis thereof, and the power tool further has a housing, a motor arranged in the housing and a main shaft driven by the motor. The main shaft has a rotating axis and an eccentric portion offset from the rotating axis. A coupling fork is driven by the main shaft and is operatively connected to a working unit. The coupling fork has one end pivotally connected to the working mandrel and the other end formed with a pair of branched forks and coupled on the eccentric portion of the main shaft. The working mandrel is generally perpendicular to the rotating axis of the main shaft, and the rotation of the main shaft around the rotating axis is converted into the pivoting motion of the coupling fork along the working mandrel so as to force the working mandrel to move and drive the accessory to work. If the user installs different accessories to the working mandrel, many different operating functions may be obtained. The common accessory may include a straight saw blade, a circular saw blade, a triangle grinding plate or scraper, etc., thereby performing different operations, such as sawing, cutting, grinding or scraping, etc.
However, as for the accessory clamping mechanism of the above described power tool, in the releasing process, the user needs to remove the clamping shaft and the accessory simultaneously, and similarly in the clamping process, the user needs to clamp the clamping shaft and the accessory to the working mandrel simultaneously, thus this clamping method is seen to be inconvenient to operate. Additionally, once the user loses the clamping shaft incautiously, the accessory clamping mechanism cannot work, and neither can the power tool comprising the accessory clamping mechanism. Moreover, due to the complex structure, the accessory clamping mechanism needs a great number of members and thus the cost is relative high.
Additionally, there is another power tool having an accessory clamping mechanism, which comprises a body with a motor mounted therein; a clamping assembly having a first clamping member which can move between a closed position in which the clamping assembly holds the accessory and an opened position in which the first clamping member of the clamping assembly is deviated from the accessory so as to remove the accessory from the clamping assembly and the first clamping member remains attached to the clamping assembly; and an actuating member having an operating member and movably attached to the body between a first position in which the clamping assembly is in the closed position and a second position in which the movement of the operating member of the actuating member causes the clamping assembly to move to the opened position.
However, when the accessory clamping mechanism is used to clamp an accessory, an end portion of the accessory needs to pass through the working mandrel, thus the end portion of the accessory is provided with an open-ended aperture so as to be clamped and released, but it cannot clamp and release an accessory with an close-ended aperture, and thus the universality of the accessory clamping mechanism is reduced.